Injection apparatus

ABSTRACT

An injection apparatus includes a counter wheel ( 54 ) that is incremented by the dose delivery mechanism each time the device is fired. The apparatus includes a final dose disabling mechanism that prevents further usage once the final dose has been delivered. An anti-tamper feature is provided to prevent inadvertent or premature initialisation of the apparatus.

This invention relates to injection apparatus, and in particular, thoughnot exclusively, to injection apparatus designed to allow a number ofdoses to be delivered from a single cartridge or syringe over a periodof time.

In many therapies a drug needs to be injected at daily or other periodicintervals. A potential problem arises because the user may not recallclearly whether they have taken a particular dose. There is therefore aneed in such apparatus to provide an increment counter, or day of theweek indicator, which indicates whether they have taken the dose for aparticular period. Also, where a fixed volume dose is delivered eachtime, it is highly desirable to be able to signal to the user when alluseable doses have been taken from the device to prevent a user frominadvertently taking a nil or incomplete dose. Although it is common onvariable dose devices to provide a counter display to allow a user todial in the number of units of medicament they wish to inject, thesedisplays only indicate the magnitude of the dose to be delivered, andreturn to zero on completion of an injection. They do not indicate adose application count i.e. the accumulated number of injections thathave been performed by the device.

In EP-A-1463550, we describe a dose application counter for an injectiondevice having a dose counter member which has a lost motion connectionto the dose setting element, so that, as a user sets the amount of thedosage volume prior to firing the device, the dose application counteris incremented by one count, irrespective of the number of units makingup the dose. Although this is a good design, it increments the count onsetting of the dose rather than actual delivery of the dose. It ispossible therefore that if a user is distracted between the setting doseand delivering it, the dose application counter suggests that the dosefor that period has already been taken. Also, after the device has beenfired to deliver the final available dose, the dose setting knob canstill be rotated to set a further dose even though subsequent firing ofthe device will not deliver a proper dose.

Accordingly, we have designed an injection device in which a countermember is incremented in response to movement of the drive member thatdelivers the does and which is therefore incremented by dose deliveryrather than dose setting.

In one aspect this invention provides an injection apparatus including adrive arrangement actuatable to allow movement of a drive member todeliver a dose upon each such actuation, and a counter member drivinglyconnected to said drive member for being incremented by each dosedelivery.

In this arrangement, a cumulative dose count may be kept by incrementingthe counter by a single uniform amount indicative of a usage,irrespective of the dose magnitude.

Although the movement could be linear it is preferred for said drivemember to be mounted for rotary movement and to rotate to deliver adose. Thus the drive arrangement may include an elongate drive plungerthreadedly engaged with said drive member and adapted to be advancedlongitudinally to deliver a dose upon corresponding rotary movement ofsaid drive member.

There are numerous ways in which actual delivery of a dose increments ortrips or counter mechanism to increment by suitable motion transfer. Forexample, the counter member may comprise a counter wheel having atoothed surface meshing with an idler cog, with said drive membercarrying one or more cog teeth for engaging the teeth of the idler cogto increment the counter wheel during each dose delivery. Although thedrive member cog teeth could be in continuous engagement with the idlercog, or the counter wheel itself, said drive member cog teeth preferablyengage the idler cog intermittently, once per dose delivery. It will beappreciated that incrementing may occur at any time during a dosedelivery cycle, but it is preferred for said counter member to beincremented part way through the cycle. Alternatively, otherarrangements may be used where movement of the dose delivery mechanismor a component thereof is used to increment a counter by one unit duringor on completion of dose delivery. This could be tripped by interactionof the plunger with a counter, or by similar interaction between any oneor more of the components in the dose delivery mechanism.

Conveniently, said drive mechanism includes a dose setting element forbeing manually twisted to energise an energy storage device associatedwith said drive member, and a releasable trigger for holding andreleasing said drive member in and from its energised condition.

The injection apparatus may conveniently include a final dosearrangement for blocking movement of said dose setting element aftersaid drive plunger has advanced to a final dose position, thereby toprevent further dose setting.

Where said drive arrangement includes a drive transfer element thatrotates with, or is integral with, said dose setting element and isconnectable to said drive member by a latching arrangement, the drivetransfer element and the plunger may have associated therewithrespective abutments that move into a blocking configuration when thedrive plunger advances towards its final dose position, therebysubstantially preventing rotational movement of the dose setting elementand thus further dose setting movement.

The apparatus may be designed to deliver fixed volume doses, or it maybe adapted to deliver doses of adjustable volume.

The final dose disabling feature may be used on devices that do not havea dose delivery counter. The invention therefore extends to an injectionapparatus including a drive arrangement having

-   -   a rotary drive gear threadedly engaged with an elongate threaded        plunger to advance said elongate plunger to deliver a dose,    -   a rotary dose setting element angularly movable against a bias        from a rest position to an energised position in which it is in        latching engagement with or latches with said rotary drive gear,    -   a trigger arrangement adapted to hold and release the drive gear        for rotary movement,    -   wherein respective abutments associated with the drive plunger        and the dose setting element move into a blocking configuration        when said elongate plunger advances after successive doses to a        final dose position, thereby preventing return of said rotary        dose setting element to its latched, energised condition.

The abutments may comprise respective cooperable lugs on the driveplunger and on the dose setting element, which cooperate to constrain orlimit rotation of said dose setting element.

Where the injection apparatus includes a housing having two relativelymovable parts required to be moved relative to one another in aninitialisation step prior to actuation to deliver a dose, for example tomix a multi-component drug, or to cock or to prime a device, it mayinclude an anti-tamper arrangement to prevent said relative movementprior to release of the anti-tamper arrangement.

Said anti-tamper arrangement may typically comprise a removable packagefor containing at least part of said device and adapted to hold saidmovable parts against initialisation movement, prior to removal of saidpackage.

Alternatively said anti-tamper arrangement may comprise a spacer elementdisposed to prevent said initialisation movement and removable from theapparatus.

The removable spacer element may comprise a tear off band, a tear offlabel, or a removable spacer element is integrally formed with one ofsaid housing parts e.g. by moulding.

The invention also extends to an injection device comprising a housinghaving two relatively movable parts required to be moved relative to oneanother in initialisation step, prior to actuation to deliver a dose,and including an anti-tamper arrangement to prevent said relativemovement prior to release of said anti-tamper arrangement.

The invention also extends to an injection device that is set or primedand which includes an externally visual indicator that displays a changein colour or other visual characteristics when said device is set orprimed.

Whilst the invention has been described above, it extends to anyinventive combination of the features set out above or in the followingdescription, claims or drawings.

By way of example only, various embodiments of the invention will be nowbe described in detail, reference being made to the accompanyingdrawings in which:

FIG. 1 is a perspective view of an injection device in accordance withan embodiment of this invention in its as supplied form, prior toretraction of the housing to reconstitute the drug;

FIG. 2 is a view similar to FIG. 1 but showing the device afterreconstitution of the drug and once two doses have been delivered;

FIG. 3 is a detailed view on the front end of the device of FIGS. 1 and2 showing the collar in a forward position;

FIG. 4 is a view of the drive mechanism removed from the remainder ofthe device, with certain parts removed;

FIG. 5( a) is an exploded view of the drive mechanism, and FIGS. 5( b)and (c) are details thereof;

FIG. 6 is a detailed view on the plunger and ratchet drive shaft;

FIG. 7 is a detailed view on the aft end of the plunger;

FIG. 8 is a cross-sectional view through the ratchet drive shaft, driveplunger and the drive gear;

FIGS. 9 to 12 are views of various embodiments of an anti-tamper devicethat need to be removed prior to moving the housing from its extendedposition shown in FIG. 1 to that of FIG. 2;

FIG. 13 is a detailed view on another form of anti-tamper feature;

FIG. 14 is a detailed exploded view of part of the arrangement of FIG.13, and

FIGS. 15( a) to (c) are detailed views showing the anti-tamper featureof FIGS. 13 and 14 at various stages of operation.

The embodiment of injection device illustrated in the drawings isdesigned for use with a medicament which is supplied as two componentsin unmixed form in a dual chamber cartridge of known type as described,for example, in our earlier application WO2007/132191. As supplied, thecartridge has two spaced bungs which define two separate chambers andthe drug is mixed by driving the rearward bung forwardly so that itcauses the forward bung to move forwardly to reveal and open a bypassslot and thereafter to force the fluid in the rear chamber into thefront chamber to mix with the substance. In such devices an initiallongitudinal movement is required to reconstitute the drug whereafterthe normal metered doses are required. In the embodiment described belowthe doses are all of a uniform volume but it will be appreciated thatthe device may easily be modified to provide a facility to deliver dosesof variable volume.

Referring to FIG. 1, the injection device comprises a housing made up ofa rear part 10 and a forward part 12 telescopically mounted on a reduceddiameter position of the rear part. A drive unit 14 is secured to therear end of the rear housing part 10, and has a rotatable dial 16 at itsrear end which is twisted to cock the device, and an actuator button 18is slid forwardly to fire the device. The rotatable dial has a forwardflange 11 that underlies the rear rim 13 of the outer shell 15 of thedrive body. The rear rim is opaque apart from three transparent windows17. The flange 11 of the dial has coloured patches 11′ disposed so that,when the dial 16 is in the cocked position, the patches 11′ align withthe windows 17 to indicate a colour change to show readiness.

At the front end of the forward housing 12 there is a sprung loadedcollar 20 having a bayonet interlock which allows it to be twisted andreleased forwardly under the influence of a spring 21 to reveal aninspection window through which the contents of the cartridge 19 may beviewed. The collar 20 also shrouds a needle hub (not shown) whenattached to the threaded portion 22 at the front end of the cartridge.

Referring now to FIGS. 4 to 8, the drive mechanism will now be describedin more detail. The dial 16 is fixed to the rear end of a ratchet driveshaft 24 for rotation therewith. At its forward end, the ratchet driveshaft carries a ratchet tooth 26 (see FIGS. 5( a), (c) and 6) thatcooperates with corresponding inwardly facing latch teeth or recesses 30on a drive gear 32 (see FIG. 8). A torsion spring 34 is anchored at itsrear end to the dial 16 and at its forward end to a fixed support collar36 which is fixed to the housing of the device. The ratchet drive shaft24 is free to rotate inside the fixed support collar 36 but is limitedto less than one turn of rotation by the interaction of an external rib37 carried by the ratchet drive shaft 24 and internal ribs 39 carriedwithin the support collar 36. The body 10 has a pair of inwardlydirected splines (not shown) that cooperate with correspondinglongitudinal grooves 40 formed in the threaded portion 42 of a plunger44 to hold the plunger against rotation but to allow longitudinalmovement thereof.

The drive gear 32 carries at 120° intervals around its surface threepairs of teeth 46 for incrementing a dose counter mechanism as to bedescribed below. Forwardly of the teeth 46, the drive gear has aplurality of latching recesses 48 which cooperate with latching splines50 on the forward end of the actuator button 18. The actuator button 18is angularly fixed with respect to the housing and axially movablebetween a rear position in which the splines 50 engage the latchrecesses 48 to prevent rotation of the drive gear to a forward positionin which the drive gear is released.

The drive gear carries a threaded bore 52 that is threadedly engagedwith the threaded portion 42 of the plunger 44 and so rotation of thedrive gear advances the plunger by a preset amount. The threads on theplunger and the bore are multi-start, for example, 4-start threads.

In use, the device is cocked or energised by twisting the dial 16through a third of a turn to wind up the torsion spring 34 and to rotatethe ratchet drive shaft 24 until the ratchet tooth 26 locks in therespective latching recess 30 on the drive gear 46. The drive gear 32 inthis position is held against rotation by the splines 50 on the actuatorbutton. In this condition the change in status is registered by thecolour change in windows 17 adjacent the dial 16. Pushing the actuatorbutton 18 forwardly releases the drive gear 32 so that it rotates withthe ratchet drive shaft 24 under the influence of the torsion spring 34,advancing the plunger 44.

A counter wheel 54 is mounted concentrically with the drive gear 32 bymeans of spaced mounting plates 56 which also mount an idler gear 58which meshes with an inner toothed track 60 on the inside of the counterwheel 54. The plates 56 are angularly fixed with respect to the housingand, as the drive gear 32 rotates, the teeth 46 trip the teeth of theidler cog 58 which in turn rotates the wheel by a uniform increment toregister delivery of a dose and to keep a cumulative count.

As in seen in FIG. 7, the rear end of the plunger is formed with twolugs 60 which, as the plunger reaches its fully extended position engageor move between lugs 62 on the inside of the ratchet drive shaft 24thereby restricting or preventing further rotation of the ratchet driveshaft relative to the plunger. This not only blocks further forwardmovement of the plunger, but also prevents the ratchet drive shaft fromrotating relative to the housing. This means that the dial 16 is lockedagainst rotational movement, subject to a small amount of backlash.

As can be seen from FIGS. 1 and 2, in order to prepare the device forinjection, the forward housing part 12 needs to be slid rearwardly to besnap locked to the rear housing 10. In doing so, this causes the plungerto act on the rear bung (not shown) in the dual chamber cartridge 21 toeffect mixing of the medicament. In order to provide a tamper evidentfeature and also to prevent inadvertent or premature mixing orreconstitution, the device of FIGS. 1 to 8 may be provided with ananti-tamper arrangement. Thus, in FIG. 9, the injection device isenclosed in plastics or similar removable casing halves 72, 74 whichprovide a recess 76, the opposed edges of which prevent telescopicmovement of the forward and rearward housing parts.

In FIG. 10, a separate plastic component 76 is heat staked around therear housing part 10, preventing telescopic movement of the housingparts until removal of the plastic component.

In FIG. 11, a peelable stick on label 78 is wrapped around the device toprevent the telescopic movement.

In FIG. 12, a moulded-end tear-off part 80 is integrally moulded withthe front housing 12 and designed to be ripped off. The adjoining regionbetween the tear-off part of the front housing may have recesses 82 toprevent sharp edges from being exposed.

Turning now to FIGS. 13 to 15, in this arrangement a raised leg 84 isformed on the rear housing part 10 and cooperates with a profiled slot86 in the rim of the forward housing part 12. In this arrangement theslot 86 is profiled so as to have a camming surface 88 up which theforward part of the leg 84 rides during initial turning movement toprovide a resilient detent action (FIGS. 15( a) to 15(b)). Having riddenup the cam surface 88 the forward part of the leg 84 is aligned with themain portion of the slot 86 so that the forward housing part 12 can beslid telescopically back to meet an opposed surface of the rear housingpart. The leg 84 widens towards its rear end so that, having moved tothe telescoped position shown in FIG. 2 (FIG. 15( c)) it snapsirreversibly into the slot so it is not then possible to slide theforward housing part 12 forwardly.

1. An injection apparatus including a drive arrangement (14) actuatableto allow movement of a drive member (32) to deliver a dose upon eachsuch actuation, and a counter member (54) drivingly connected to saiddrive member (32) for being incremented by each dose delivery.
 2. Aninjection apparatus according to claim 1, wherein said drive member (32)is mounted for rotary movement and rotates to deliver a dose.
 3. Aninjection apparatus according to claim 2, wherein said drive arrangementincludes an elongate drive plunger (42) threadedly engaged with saiddrive member (32) and adapted to be advanced longitudinally to deliver adose upon corresponding rotary movement of said drive member (32).
 4. Aninjection apparatus according to claim 2, wherein said counter membercomprises a counter wheel (54) having a toothed surface (60) meshingwith an idler cog (58), and said drive member carries one or more cogteeth (46) for engaging the teeth of the idler cog (58) to increment thecounter wheel (54) during each dose delivery.
 5. An injection apparatusaccording to claim 4, wherein said drive member cog teeth (46) engagethe idler cog (58) intermittently, once per dose delivery.
 6. Aninjection device according to claim 1, wherein said counter member (54)is incremented part way through a dose delivery cycle.
 7. An injectionapparatus according to claim 3, wherein said drive mechanism (14)includes a dose setting element (16) for being manually moved toenergies an energy storage device (34) associated with said drive member(32), and a releasable trigger (18) for holding and releasing said drivemember in and from its energized condition.
 8. An injection apparatusaccording to claim 7, including a final dose arrangement (60, 62) forblocking movement of said dose setting element (16) after said driveplunger has advised to a final dose position, thereby to prevent furtherdose setting.
 9. An injection apparatus according to claim 8, whereinsaid drive arrangement (14) includes a drive transfer element (24) thatrotates with, or is integral with, said dose setting element (16) and isconnectable to said drive member (18) by a latching arrangement (26,30), with the drive transfer element (24) and the plunger (42) havingassociated therewith respective abutments (60, 62) that move into ablocking configuration when the drive plunger (42) advances towards itsfinal dose position, thereby substantially preventing further dosesetting movement.
 10. An injection device according to claim 7,including an externally visible color change indicator for indicatingwhen said drive is in the energized condition.
 11. An injectionapparatus according to claim 1, adapted to deliver fixed volume doses.12. An injection apparatus according to claim 1, adapted to deliverdoses of adjustable volume.
 13. An injection apparatus including a drivearrangement (14) having a rotary drive gear (32) threadedly engaged withan elongate threaded plunger (42) to advance said elongate plunger todeliver a dose, and a rotary dose setting element (16, 24) angularlymovable against a bias from a rest position to an energized position inwhich it latches with said rotary drive gear (32), and a triggerarrangement (18) adapted to hold and release the drive gear for rotarymovement, characterized by respective abutments (60, 62) associated withthe drive plunger (42) and the dose setting element (16, 24) that moveinto a blocking configuration when said elongate plunger (44) advancesafter successive doses to a final dose position, thereby preventingreturn of said rotary dose setting element to its latched, energizedcondition.
 14. An injection apparatus according to claim 13, whereinsaid abutments comprise respective co operable lugs (60, 62) on theelongate plunger (44) and on the dose setting element (16, 24), whichcooperate to constrain rotation of said dose setting element.
 15. Aninjection apparatus according to claim 13, including a housing havingtwo relatively movable parts (10, 12) required to be moved relative toone another in an initialization step prior to actuation to deliver adose, and including an anti-tamper arrangement (70, 76 etc) to preventsaid relative movement prior to release of the anti-tamper arrangement.16. An injection device according to claim 15, wherein said anti-tamperarrangement comprises a removable package (70, 72) for containing atleast part of said device and adapted to hold said movable parts againstinitialization movement, prior to removal of said package.
 17. Aninjection device according to claim 16, wherein said anti-tamperarrangement comprises a spacer element disposed to prevent saidinitialization movement and removable from the apparatus.
 18. Aninjection device according to claim 17, wherein said removable spacerelement comprises a tear off band (76).
 19. An injection deviceaccording to claim 17, wherein said removable spacer element comprises atear off label (78).
 20. An injection apparatus according to claim 17wherein said removable spacer element (80) is integrally formed with oneof said housing parts.
 21. An injection device comprising a housinghaving two relatively movable parts (10, 12) required to be movedrelative to one another in an initialization step, prior to actuation todeliver a dose, and including an anti-tamper arrangement (70, 76 etc) toprevent said relative movement prior to release of said anti-tamperarrangement.
 22. An injection apparatus according to claim 1, whereinsaid drive mechanism (14) includes a dose setting element (16) for beingmanually moved to energize an energy storage device (34) associated withsaid drive member (32), and a releasable trigger (18) for holding andreleasing said drive member in and from its energized condition.